1. Field of the Invention
The present invention generally relates to testing circuit. In particular, the present invention relates to a circuit to control operation of a functional circuit based on a test result.
2. Description of the Related Art
Semiconductor fabricated integrated circuits (IC) typically undergo three separate test cycles before die separation: (1) in process testing, such as continuous monitoring of sheet resistivities, junction depths, and other pertinent device parameters, such as current gain and voltage breakdown; (2) a preliminary electrical testing called the wafer-probe or the wafer-sort test performed prior to the scribing and the die-separation steps; and (3) a detailed testing of all pertinent circuit parameters after the completion of the assembly and the packaging operations.
The wafer-probe test, also called the wafer-sort operation, takes place after the wafer processing is completed. It is then followed by the die-separation (scribing) where the water is cut apart and each die is physically separated. These tests are usually made with multi-probe instruments which have adjustable probes to contact the bonding pads of the die to be tested. Each individual die undergoes a number of basic electrical tests. If found defective, it is marked with an ink marker for identification, to be discarded after the die-separation step. In this manner, each and every die on the wafer gets tested prior to the start of the assembly operation.
The wafer-sort testing step and the assembly step may or may not take place at the same manufacturing facility Customers may purchase wafers after the wafer-sort testing and performs the assembly operations to build the separated dice into their products. In the assembly process, failed dice may be erroneously introduced into the product either as a result of the non-inking or assembly process or any other reason. As a result, dice that failed operational specifications may be used in a product resulting in a high product failure rate. A high product failure rate increases the costs associated with returned products.
Accordingly, there is a need in the technology of IC testing to prevent a bad die from being used when integrated into a product.